Electric heating apparatus



April 4, 1939. E. N. CALHOUN 2,152,953 7 ELECTRIC HEATING APPARATUS Filed Aug. 18, 1958 2 Sheets-Sheet l .61 I fi 7 2;, Mm 4 Q J 4 iff I d! v 46a 6a;

' ya L 14/ Ernzat N. Calhoun I-v--rox 115 MM /m AT To RN 213 April E. N. CALHOUN 2,152,953

ELE CTRIC HEATING APPARATUS I Filed Aug. 18, 1938 2 Sheets-Sheet 2 19% 1% m M my Us! 15W 1% 15W 1% 15 g, y l w/ L147 M M1 INVSLNT R.

B flaw, M MMQ ATTFDRNEDES Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE ELECTRIC HEATING APPARATUS ErnestrN. Calhoun, Pittsburgh, Pa .assiznor to Edwin L. Wiegand, Pittsburgh, Pa.

24 Claims.

My invention relates to electric heating apparatus. One use to which my invention may be put is in connection with electric cooking ranges, or the like. The principal object of my invention is to provide new and improved apparatus of these types. This application is a continuation in part of my application Serial Number 79,515, filed May 13, 1936.

In the drawings accompanying this specification, and forming a part of this application, I have shown, for purposes of illustration, several forms which my invention may assume. in these drawings:

Figure 1 is a diagrammatic view of electric heating apparatus embodying my invention, and

Figures 2, 3, 4, 5, and 6 are diagrammatic views of other embodiments of my invention.

In Figure 1 there is shown, diagrammatically, an electrical heating device lil'connectable to a so source of current through control switch means i l. The heating device It is here shown as comprising a plurality of unitary heating elements,

in this instance two, l2, It. The unitary heating elements l2, 03 are here shown as each of 25 annular form, one of which, [2, is 01' larger diameter than the other, l3, and is adapted to be disposed around and concentric with the smaller annular element. The heating elements l2, 53 are here shown as comprising resistors it, t l) which may be embedded in compacted granular refractory insulation in annular metallic sheaths it, 871', these sheaths being diagrammatically indicated by dot and dash lines.

The control switch means it is here shown as including a pair of movable switch elements l9 pivotally mounted and electrically connected to pivots 2K1, ii. The movable switch elements l8, it are here shown as adapted to assume four positions, which may be identified as a, b, c, and d, in accordance with the suiiixes of the refer= ence numerals of the relatively stationary oontacts to be described, The first position is an open position, indicated by the insulating spots 22a, 23a.

In the second position, b, the movable switch element it is adapted to make contact with a contact 24b connected with a line conductor ill, which in this instance is the neutral conductor of a three wire source of current having outside conductors t2, 3. The three wire sources desirably provides an electromotive force between an outside conductor and the neutral conductor of half that between the outside conductors. Also, in the second position, b, the switch ele= ment it is on an insulating spot 25?).

In the third position, 0, the switch element I8 is on an insulating spot 260, while the switch element I 9 is adapted to make contact with a contact 210. The contact 210 is here shown as connected to the line conductor tit, through a 5 jumper 30 connecting the contact tie with another contact 29d, the latter being connected through a conductor 3i, to the line conductor t3. In the fourth position, (1, the switch element It is adapted to engage a contact 26d, which is connected, through a conductor 38, to the line conductor 43, while the switch element !9 is adapted to engage the contact 29d.

The outer line conductor, 42, is here shown as. connected to a terminal 3i of the resistor l4, and this terminal, 3!, is in turn connected, through a conductor 32, to a terminal 33 of the resistor 15.

The other'terminal, 3 3, of the resistor M is connected, by a conductor 35, to the pivot 2! of the switch element i9,- whereas the other terminal, 36, of the resistor I5 is connected, through a conductor til, to the pivot 200i the switch element it.

The switch elements l8, l9 are here shown as operable in unison by an insulating cross bar Ml.

The operation of the embodiment of the invention shown in Figure 1 is as follows. When the control switch means it is moved to its first operative position, b the resistor it is connected directly across the neutral conductor ii an and the outside conductor it, while the resistor M is not supplied with current at all. In the operative position 0 of the control switch means it, the resistor it is connected across the two outside line conductors iii, 63, whereas the resistor l is not supplied with current. In the third operative position, d, the resistors it, it are in parallel across the outside line conductors L12,

llhe resistors It, iii are desirably so designed 40 that each one of them will operate at its full heating capacity when the greatest available electromotive force is impressed thereon, so that if, byway of example, each or" the resistors i i, i5 is designed to operate at its full heating capacity at 230 volts, both resistors will consequently operate at full heating capacity when the control switch-means if] is in position at, assuming that the electromotive force between the two outside conductors as, 43 of the three wire system is 230 54) volts. By way of further example, if each of the resistors i l, is designed to dissipate 1000 watts at 230 volts, then oi course the heating device it will emit heat the rate of 2000 watts when the control switch means ii is in position d. Ii 5% the heating device 10 is utilized in a cooking range this high heat may be utilized as and when desired and the distribution of heat will be such that a high heat is applied to a maximum area or the object to be heated. On the other hand, when the control switch means is in position c, the heating device ill will emit heat at the rate of 1000 watts. and. in the instance shown, the distribution of heat emission is or course changed, and is localized in the annulus defined by the outer heating element [2. This latter rate and distribution of heat is particularly adapted for heating trying pans and griddles. When the control switch means I i is in position b only the central heating element 13 is in operation, and inasmuch as it has been assumed that the heating element I3 is designed to operate at full capacity at 230 volts, it will operate at a quarter of its capacity when 115 volts is impressed thereon, as will be the case when the control switch means is in position b. Consequently, the heating device ill will emit heat at the rate oi. only 250 watts and this heat is localized in the annulus which is defined by the central heating element It. The heating device is then particularly adapted for heating ob Jects where a low rate of heat transfer is desired, as, tor example, in simmering.

While the apparatus illustrated in Figure 1 has been described in connection with annular heating elements, .it will be understood that while particular advantages flow from the useof such elements, other forms of elements may be utilized. Furthermore, as will be apparent to those skilled in the art, if it is found desirable in connection with the uses to which the heating apparatus is to be put, that the order in which the heating elements are connected to the source oi. current may be changed so that, for example, the outer heating element I! may be connected across an outside conductor, as at 42, and the neutral conductor 4|, to secure a low rate of heat emission, and the inner heating element [3 may be next connected across the outside line conductors 42, 43, to secure heat emission at the full capacity of that element, and then both heating elements 12, I! may be connected across the outer line conductors 42, 43 to secure heat emission from both heating elements at full capacity. In view of the foregoing, other arrangements will readily suggest themselves to those skilled in the art.

Figure 2 shows another embodiment 01' my invention in which two resistors 44, 45 are connectable to a three wire source of current, represented by conductors 4B, 41, 45, through control switch means 49, in various ways. The resistor 44 has one terminal connected, through a conductor 50, to the line conductor 41 and the other terminal connected to the pivot of a movable switch element iii. The other resistor 45 has one terminal connected, through a conductor 52, to the line conductor 48 and the other terminal connected to the pivot of a movable switch ele ment 53, here shown as movable in unison with the switch element 5| through an insulated connecting bar 54. In the position of the control switch means 48 shown in Figure 2, the switch elements 5 l, 53 are in engagement with insulating spots 55a, 58a and the resistors 44, 45 are therefore not supplied with current.

In the next position, b, the switch element 5| is adapted to engage a contact 51b which is here shown connected by means of a jumper 69 to a contact Sld, the Jumper 69 being in turn connected, by a conductor 10, to the neutral conduccampus tor 44 of the three wire supply. In this position (b) the switch element 53 engages an insulating spot llb.

In the next position, c, the switch element II engages an insulating spot He, whereas the switch element 53 engages a contact 60c, which is here shown as connected by a Jumper 1i to a contact 82d, which is in turn connected, by a conductor 12, to the neutral conductor 46.

In the next position, d, the switch element 5| engages the contact Bid, and the switch element 53 engages the contact 52d.

In the-next position, e, the switch element 5| engages a contact 53c, here shown as connected, by a conductor 13, to the outside line conductor 48, while in this position of the switch means the switch element 53 engages an insulating spot 84c.

In the next position, I, the switch element 5! engages an insulating spot 85!, whereas the switch element 53 engages a contact 85], which is here shown as connected, by a conductor 14, to the outside line conductor 41.

- In the next position, a, the switch element 5| engages a-contact 61g, which is connected by means of a jumper 15 to the contact 53a and therefore to the line conductor 48, whereas in this same position the switch element 53 engages a contact 889, here shown as connected by a Jumper 16 to the contact 86 and therefore to the line conductor 41.

The operation of the apparatus shown in Figure 2 may be best described by assuming particu lar values of watts dissipated by the resistors 44, 45 and voltages supplied by the line conductors 46, 41, 48. Assuming that the resistor 45 is designed to dissipate 1200 watts when an electromotive force of 230 volts is impressed thereon and that the resistor 44 is designed to dissipate 800 watts when an electromotive force of 230 volts is impressed thereon, and further, that the electromotive force between the neutral conductor 46 and either one of the outside conductors is 115 volts, then when the control switch means 49 is in position b, the resistor 44 is connected across the line conductor 41 and the neutral conductor 46, and therefore, since it is being operated at one-half its rated voltage, it will dissipate 200 watts. The other resistor, 45, is not being supplied with current. In the next position, c, the resistor 44 is not being supplied with current but the resistor 45 is connected across the line conductor 48 and the neutral conductor 48 and is therefore being supplied with one-half rated voltage and consequently dissipates 300 watts. In the next position, (1, the resistor 44 is again connected across the line conductor 41 and the neutral conductor 46, and the resistor 45 is con nected across the line conductor 48 and the neutral conductor 46. The resistor 44 therefore dissipates 200 watts whereas the resistor 45 dissipates 300 watts, so that the total dissipation from the two resistors together is 500 watts. In the next position, e, the resistor 44 is connected across the outside line conductors 41, 48 and therefore has 230 volts impressed thereon and operates at its full rate of capacity 01 800 watts; the resistor 45 is not supplied with current. In the next position, I, the resistor 44 is not supplied with current, but the resistor 45 is connected across the outside line conductors 41, 48 and therefore operates at its full rate of capacity of 1200 watts. In the next position, 9, both resistors 44, 45 are connected across the outside line conductors 41, 48, in parallel, and therefore each operates at its full rated capacity, so that the total dissipation of the two resistors together is 2000 watts.

It will of course be apparent that the two resistors 44, 45 may be utilized to heat the same object, and furthermore, if desired, they may be embodied in annular heating elements Just as are the resistors I4, I in the embodiment of Figure 1. If the resistor 45 is selected as that one embodied in the outer annular heating element and the resistor 44 is selected as that one embodied in the inner annular heating element, it will be apparent that in the first heating position, b, the inner resistor 44 will supply a low heat; in

- position 0 the outer resistor 45 will supply a higher heat; in position at both resistors 44, 45, acting together, will supply a still higher heat; in position e the inner resistor 44 will supply a still higher heat; in position 1 the outer resistor 45 will supply a still higher heat, whereas in position 9, the two resistors 44, 45 together will supply a maximum heat.

In the embodiment shown in Figure 3 a resistor II has one terminal connected, by a conductor I8, to an outside line conductor IOI of a three wire supply and its other terminal connected to the pivot 01 a switch element 80. Another resistor, 0i, has one terminal connected to the pivot of another switch element, 02, and its other terminal connected to the pivot of still another switch element 03. The switch elements 80, 82, 83, as here shown, are operable in unison by means of an insulated connecting bar III. In the position shown in Figure 3 all of the switch elements, 80, 02, 83, are in engagement with insulating spots 05a, 06a, tIa, respectively, and neither of the resistors '11, BI is therefore supplied with current.

In the first operative position, b, the switch element is in engagement with a contact 88b. The contact 88b is here shown as connected by means of a jumper 91 to a contact b which in this position is engaged by the switch element 83. Also, in this position the switch element 82 engages a contact 8% which is connected, by a conductor 90, to a tap, which may be adjustable, on an auto transformer 99. The terminals of the auto transformer 99 are here shown as connected to the line conductor IIII and tothe neutral conductor I00 of the three wire supply.

In the next position, 0, the switch element 80 is in engagement with a contact 9Ic, here shown as connected by means of a jumper I03 with a contact 90d, in turn connected, by a conductor I00, to the neutral conductor I00. In this same position the switch elements 92, 83 are in engage ment with insulating spots 92c, 930.

In the next position, (1, the switch element 80 is in engagement with the contact 94d, whereas the switch element 82 is in engagement with a contact 95d connected, by conductor I05, to the neutral conductor I00, and the switc". element 83 is in engagement with a contact 96d connected to the outside line conductor I02.

For purposes of illustration, in describing the operation of the embodiment of Figure 3, it will be assumed, for example, that each of the resistors II, M will operate at its full capacity when an electromotive force of volts is impressed on its terminals. Let it be further assumed that each resistor has a full capacity of 1000 watts at 115 volts. In the first operative position, b, the resistors 17, 8| are connected in series with each other and if an electromotive force of 115 volts were applied to the outside terminals of these resistors, the two resistors together would dissipate a quarter of their rated capacity, that is, 500

watts. However, when the control switch means is in the position b the series connected resistors TI, 8i do not have the full 115 volts between the line conductor I M and the neutral conductor I 00 applied thereto, but only a fraction thereof, as determined by the position of the tap on the auto transformer 99. By way of example, if it is desired that the two series connected resistors shall dissipate 200 watts, the tap will be so selected that approximately 70 volts will be applied to the series connected resistors 11, 8|. In the next position, 0, of the control switch means the resistor I1 is connected across the line conductor IN and the neutral conductor I00 and therefore operates at its full rated capacity of 1000 watts. In this position the resistor BI is not supplied with current. In the next position, d, the resistor TI is again connected across the line conductor IOI and the neutral conductor I00 and the resistor 8| is connected across the line conductor I02 and the neutral conductor I 00. Both resistors I1, 8| consequently operate at their full rated capacity, and

together dissipate 2000 watts.

In the embodiment shown in Figure 4 a resistor I06 has one terminal connected to an outside line conductor I3l of a three wire source and has ,its other terminal connected to the pivot of a switch element I07. Another resistor I08 has one terminal connected to the other outside line conductor I32 01' the three wire source and its other terminal connected to the pivot of a switch element I09. An auto transformer I I0 is here shown as having one terminal connected to the neutral conductor I30, and, if desired, the supply of current through the auto transformer may be controlled by-a switch comprising a switch element III having a contact 51) connected to the other terminal of the auto transformer IIO, the switch element III being connected, by a conductor I24, to the line conductor I 3| The switch elements II I, I01, I09 are here shown as operable in unison by means of an insulated connection bar I 25.

In the position shown in Figure 4 the switch ele-- ments III, I01, I09 are in engagement with insulating' spots 2a., III-3a, II4a, respectively, and no current is supplied to the resistors I06, I08. In the first operative position, b, the switch element III engages the contact II5b, the switch element I01 engages'a contact II6b, here shown as connected, by a conductor I26, to a tap on the auto transformer I I0, whereas the switch element I09 is in engagement with an insulating spot IIIb. In the next position, 0, the switch elements III, I01 engage insulating spots H80, H90, respectively, whereas the switch element I09 engages a contact I200, here shown as connected, by a conductor I21, to the neutral conductor I30. In the next position, d, the switch element III engages an insulating spot I2Id, whereas the switch element I01 engages a contact I22d, here shown as connected, by a conductor I28, to the neutral conductor I30; and in the same position of the control switch means the switch element I09 engages a contact I23d, here shown as connected by a jumper I29 with the contact I200 and therefore connected to the neutral conductor I30.

In considering the operation of the embodiment of Figure 4;, it may be assumed again that resistors I06, I08 are each so designed that when an electromotive force of H5 volts is impressed, each resistor will operate at full rated capacity of 1000 watts. In the first operative position, b, the switch element III engages the contact II5b and connects the auto transformer I I0 across the line conductor I 3| and the neutral conductor I30, whereas the switch element I01 engages the contact I lib and consequently causes an electromotive force to be applied to the resistor I00 depending upon the position of the tap to the auto transformer I I0. If it is desired that the resistor I shall dissipate, for example, approximately 200 watts, the tap of the auto transformer H0 is so positioned that approximately 50 volts will be supplied from the auto transformer IIO to the resistor I06. In the next position, 0, of the control switch means the auto transformer H0 is disconnected from the circuit and the resistor III is not supplied with current, whereas the resistor I03 is connected across the line conductor I32 and the neutral conductor I30, and therefore dissipates 1000 watts. In the next position, d, of the control switch means the resistor I06 is connected across the line conductor I3I and the neutral conductor I30, whereas the resistor I00 is connected across the line conductor I32 and the neutral conductor I30. Consequently, both resistors I00, I03 operate at their full rated capacity and together dissipate 2000 watts.

What has been stated in connection with form and location of the resistors 44, 45 of the embodiment of Figure 2 applies equally well with respect to the resistors I1, 3| of the embodiment of Figure 3 and the resistors I03, I08 0f the embodiment of Figure 4.

It will be apparent that a. switch similar to the switch III of the embodiment of Figure 4 may be. added to control the auto transformer 39 of the embodiment of Figure 3.

In the embodiment shown in Figure 5 a resistor I33 has one terminal connected to an outside line conductor I34 of aFthree wire supply and its other terminal connected to the pivot of a switch element I40. Another resistor, I43, has one terminal connected to the pivot of another switch element, I, and its other terminal connected to the pivot of still another switch element I42. The switch elements I40, I41, I42, as here shown, are operable in unison by means of an insulated connecting bar I44. In the position shown in Figure 5 all of the switch elements, I40, I, I42, are in engagement with insulating spots I3Ia, I38a, I39a, respectively, and neither of the. resistors I33, I43 is therefore supplied with current.

In the first operative position, b, the switch element I40 is in engagement with a contact I311). The contact I3") is here shown as connected by means of a jumper I45 to a contact I3'Ic, the jumper I45 being connected by a conductor I46 to the other outside.conductor, I36, of the three wire supply. In position b the switch element I4I engages a contact I33b which is connected by a conductor I41 to the line conductor I34; and the switch element I42 engages a contact I39b. The contact I301) is connected by a Jumper I48 to a contact I39d which is connected to the conductor I46 and hencealso to the line conductor I36.

In the next position, 0, the switch element I40 engages the contact I310; and the switch elements I4I, I42 engage insulating spots I330, I390 respectively.

In the next position, (1. the switch element I40 engages an insulating spot I3Id; the switch element I4I engages the contact I38d which is connected by a jumper I49 to the contact I33b and hence to the conductor I41; and the switch element I42 engages the contact I39d.

In the next position, e, the switch element I40 engages a contact I3Ie which is connected by 9.

conductor I50 to the neutral conductor, I35, of the three wire supply; and the switch elements I4I,. I42 engage insulating spots I38e, I33e respectively,

In the next position, I, the switch element I40 engages a contact I31! which is connected by a jumper I5I to a contact I33 which in this position is engaged by the switch element HI; and the switch element I42 engages a'contact I301 which is connected by a conductor I52 to the neutral conductor I35.

The operation of the embodiment shown in Figure 5 is as follows. Let it be assumed, merely by way of example, that each of the resistors I33, I43 is designed to operate at full rated capacity when individually connected across the outside conductors I34, I36 of the three wire supply, and that these conductors supply a voltage of 230 volts, and that when so connected each of the resistors dissipates 1000 watts. In that case when the switch elements I40, I, and I42 are in position b, each of the resistors I33, I43 will be connected across the conductors I34, I36 and the total dissipation will be 2000 watts. In position 0 the resistor I33 will be connected across the conductors I34, I36, and the resistor I43 will not be supplied with current. Accordingly the total dissipation is 1000 watts. In position d the resistor I43 will be connected across the conductors I 34, I36, and the resistor I33 will not be supplied with current, and accordingly the total dissipation will again be 1000 watts. In this instance the resistors I33, I 43 desirably define different areas, and may be, for example, of concentric annular form as described in connection with Figure 1, and the resistor I33 may be the outer unit and the resistor I 43 may be the inner unit. Accordingly, a dissipation of 1000 watts may be obtained either in a large annulus or in a small annulus, so that, ifdesired, the smaller annulus may be used for more efllcient heating of small utensils. In position 6 the resistor I33 is connected across the conductors I34, I35 and accordingly is supplied with volts and therefore dissipates 250 watts. The resistor I43 is not supplied with current in this position. In position i the resistors I33, I43 are connected in series across the conductors I34, I35, each then dissipating 62.5 watts, so that the total dissipa tion is watts.

In the embodiment shown in Figure 6 a resistor I53 has one terminal connected to an outside line conductor I54 of a three wire supply and its other terminal connected to the pivot of a switch element I60. Another resistor, I63, has one terminal connected to a pivot of another switch element I6I, and its other terminal connected to the pivot of still another switch element I62. The switch elements I60, I6I, I62, as here shown, are operable in unison by means of an insulated connecting bar I64. In the position shown in Figure 6 all of the switch elements I60, I6I, I62 are in engagement with insulating spots I5Ia, I58a, I59a, respectively, and neither of the resistors I53, I63 is therefore supplied with current.

In the first operative position, b, the switch element I60 is in engagement with a contact I5Ib which is connected by a conductor I65 to the other outside line conductor, I56; the switch element I6I is in engagement with a contact I53b which is connected by a conductor I66 with the line conductor I54; and the switch element I62 engages a contact I59b which is connected by a jumper I61 to contacts I590, I59d, the jumper being connected by a conductor I 68 to the line conductor I56.

In the next position, c, the switch element I60 engages an insulating spot I51c; the switch element I6I engages a contact I5Bc connected by a jumper I69 to the contact I58b and hence to the line conductor I54; and the switch element I62 engages the contact I590 connected by the jumper I61 and the conductor" I68 to the conductor I56.

In the next position, d, the switch element I60 engages a contact- I 51d connected by a jumper I10 to a contact I51 in turn connected by a conductor I1I to a contact I58d, the latter being engaged by the switch element I6I in this position; and the switch element I62 engages the contact I59d.

In the next position, e, the switch element I60 engages an insulating spot I51e; the switch element I6I engages the contact I58e; and the switch element I62 engages a contact I59e connected by a conductor I12 to the neutral conductor, I55, of the three wire supply.

In the next position, 1, the switch element I60 engages the contact I51 the switch element engages a contact I5Bf which is connected by a jumper I13 to the contact I58d and hence to the conductor I1I; andthe switch element I62 engages a contact I59 connected by a jumper I14 to the contact I59e and hence to the conductor I12.

The operation of the embodiment shown in Figure 6 is as follows. Let it again be assumed that each of the resistors I53 and I63 'willioperate at full rated capacity and dissipate 1000 watts when individually supplied with 230 volts. In position I) both of the resistors I53 and I63 are connected across the conductors I54, I56, assumed to supply 230 volts, and accordingly the total dissipation is 2000 watts. In position the resistor I63 is connected across the conductors I54, I56, and the resistor I53 is not supplied with current. Accordingly the total dissipation is 1000 watts. In position (1 the resistors I53, I63 are connected in series across the conductors I56, I56, each then dissipating 250 watts so that the total dissipation is 500 watts. In position e the resistor I63 is connected across the conductors I55, I55, whereas the resistor I53 is not supplied with current. The resistor I63 being supplied with 115 volts, dissipates 250 watts. In position I the resistors I53, I63 are connected in seriesacross the conductors I54 and I55, each then dissipating 62.5 watts so that the total dissipation is 125 watts. It will of course be evident that in this embodiment as Well as in the other disclosed embodiments the resistors I53, I63 may be in concentric annular form as described in connection with Figure 1. For example, the resistor I 53 may be the outer annulus and the resistor ltd may be the inner annulus.

It will be apparent that if desirable, the re-= sistors in any one of the embodiments may be designed to operate at difierent full rated heating capacity.

In general, it should be understood that while the operation of the embodiments of the invention has been described in connection with. par ticular suitable rated capacities of: the resistors or heating elements and with respect to particular electromotive forces impressed thereon, that my invention is not limited to these particular values.

, From the foregoing it will be apparent to those skilled in the art that each of the illustrated embodiments of my invention provides a new and improved electric heating apparatus, and accordingly, each accomplishes the principal object of my invention. On the other hand, it also will be obvious to those skilled in the art that the illustrated embodiments of my invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of my invention, or sacri ficing all of the advantages thereof, and that accordingly, the disclosure herein is illustrative only, and my invention is not limited thereto.

1. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force; switch means having a plurality of movable ele ments and a common operating means for moving said elements in unison to difierent positions; and means, including electrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more of said resistors and one or more of said pairs of conductors in different relationships for said different positions of said switch means respectively.

2. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide difierent electromotive forces, the combination of: a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductorsproviding the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to difierent positions; and means, including electrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more of said resistors and one or more of said pairs of conductors in different relationships for said diiferent positions of said switch means respectively, at least one of said resistors in at least one of said positions of said switch means being connected, through said switch means, across a pair of said conductors providing an electromotive force less than said highest electromotive force.

3. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces,

the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that in one position of said .switch means at least two of said resistors are so connected to certain of said conductors that they operate at full heating caacity, and in a succeeding position of said switch means one only of said resistors is so connected to certain of said conductors that it operates at ftdl heating capacity, and in a succeeding position of said switch means one only of said resistors is connected to certain of said conductors and is so connected that it operates at less than full heatingcapacity.

4. In an electric heating apparatus connect- 75.

structed to operate at full capacity when individually connected across that pair oi. conductors providing-the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are connected across that pair of conductors providing the highest electromotive force, and in a succeeding position of said switch means one only of said resistors is connected across that pair of conductors providing the highest electromotive force, and in a succeeding position of said switch means at least one of said resistors is connected across a pair of said conductors providing an electromotive i'orce less than said highest electromotive force.

5. In an electric heating apparatus connectable to a plurality of supply line conductors different pairs of which provide diilerent electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said supply line conductors is-applied thereto; an autotransformer, having its end terminals connected to one of said pairs of supply line conductors, said pair furnishing an electromotive force substantially less than the electromotive force furnished by another pair of said supply line conductors, said autotransformer having a tap between said end terminals; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to dififerent positions; and means, including elsetrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more oi said resistors with one or more oi said pairs of supply line conductors or with said tap and one oi. said supply line conductors in diflerent relationships for said difierent positions or said switch means respectively. I

6. In an electric heating apparatus connectable to a plurality of supply line conductors difi'erent pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said supply line conductors is individually applied thereto; an autotransiormer, having its end terminals connected to one of said pairs of supply line conductors, and having a tap between said end terminals; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more of said resistors with one or more of said pairs of supply line conductors or with said tap and one of said supply line conductors in diflerent relationships for said difierent positions of said switch means respectively and in one of which relationships at least two of said resistors are connected in series across said tap and one of said line conductors.

'7. In an electric heating apparatus connectable to a plurality of supply line conductors ditierent pairs of which provide diflerent electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive ibrce corresponding to that furnished by\ a predetermined pair of said supply line conductors is individually applied thereto; an autotransiormer, having its end terminals connected to one of said pairs of supply line conductors, and having a tap between said end terminals; switch means having .a plurality of movable elements and a common operating means for moving said elements in unison to diflerent positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are soconnected to said supply line conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so connected to said supply line conductors that it operates at full capacity, and in a succeeding position of said switch means one of said resistors is connected across one of said supply line conductors and said tap and operates at less than full heating capacity.

8. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide difierent electromotive forces, the combination of: a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force, one of said resistors being constructed to operate at a full heating capacity different from another of said resistors; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, ineluding electrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more of said resistors and one or more of said pairs of conductors in different relationships for said different positions of said switch means respectively.

9. In an electric heating apparatus connectable to a plurality of conductors different pairs 01 which provide difierent electromotive forces, the combination of a plurality of resistors constructed to operate at full heating capacity when in-- dividually connected across that pair of said conductors providing the highest electromotive force, one of said resistors being constructed to operate at a full heating capacity different from another of said resistors; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to diilerent positions; and means, including electrical connections, so constructed and arranged that said switch means is adapted to inter connect one or more of said resistors of diilerent capacities to conductors providing the highest electromotive force in different relationships for different positions of said switch means, and to interconnect one or more of said resistors 01 dir- Ierent capacities to conductors providing less than the highest electromotive force in different relationships for other difierent positions of said switch means.

10. In an electric heating apparatus connectable to a plurality of conductors different pairs oi which provide diflerent electromotive iorces, the combination or: a plurality of resistors constructed to operate at full heating capacity when individually connected across a pair of conductors providing the highest electromotive force, one 0! said resistors being constructed to operate at a full heating capacity different from another of said resistors; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including. electrical connections, so constructed and arranged that said switch means is adapted to interconnect one or more of said resistors and one or more 01' said pairs of conductors in different relationships for said diiTeren-t positions of said switch means respectively, a resistor of less capacity than another of said resistors, being connected through said switch means in at least one of said positions of said switch means, across a pair of said conductors providing an electromotive force less than said highest electromotive force.

11. In an electric heating apparatus connectable to a plurality of supply conductors different pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to a plurality of different positions; means, separate from said switch means, constructed and arranged to connect one terminal of each of said resistors to a supply conductor; and means, including additional electrical connections, so constructed and arranged that said switch means is adapted to interconnect one.or more of said resistors and one or more of said pairs of conductors in different relationships for said plurality ofdifierent positions of said switch means respectively.

12. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide difierent electromotive forces, the combination of a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements'in unison to a plurality of different positions; said switch means including relatively stationary contact means with which one of said movable elements is cooperable in two different positions respectively of said element; means, separate from said switch means, constructed and arranged to connect said contact means to one of said conductors; and means, including additional electrical connections, so constructed and arranged that said switch means is adaptedto interconnect one or more of said resistors and one or more of said pairs'of con ductors in diiTerent relationships for said plurality of different positions of said switch means respectively. I

13. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to a plurality of different positions; said switch means including relatively stationary first contact means with which one of said movable elements is cooperable in two diflerent positions respectively of said element, and including also relatively stationary second contact means comprising a plurality of contacts with one of another of which said movable elements is cooperable in one of its positions; means, separate from said switch means, constructed and arranged to connect said first contact means and said one of said contacts to one of said conductors; and means, including additional electrical connections, so constructed and arranged that said switchmeans is adapted to interconnect one or more of said resistors and one or more of said pairs of conductors in different relationships for said plurality of difierent positions of said switch means respectively.

14. In an electric heating apparatus connectable to a plurality of supply conductors different pairs of which provide diflerent electromotive forces, the combination of a plurality of resistors constructed to operate at full heating capacity when individually connected across that pair of said conductors providing the highest electromotive force; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to a plurality of different positions; said switch means including relatively stationary contact means with which one of said movable elements is cooperable in two diiferent positions respectively of said element; means separate from said switch means, constructed and arranged to connect said contact means to one of said conductors; means, separate from said switch means, constructed and arranged to connectone terminal of each of said resistors to a supply conductor; and means, including additional electrical connections,- so constructed and "arranged that said switch means isadapted to interconnect one or more of said resistors and one or more of said pairs of conductors in different relationships for said plurality of 'diflerent positions of said switch means respectively.

15. In an electric heating apparatus connectable to a three wire supply system comprising main conductors and a neutral conductor, the combination of: two resistors constructed to operate at full heating capacity when individually connected across the main conductors; switch means having two movable elements and a common operating means for moving said elements in unison to a plurality of different positions; said switch means including relatively stationary first contact means with which one of said elements is cooperable in two difierent positions respectively of said element, and including also relatively stationary second contact means comprising at least one contact with which the other of said elements is cooperable in one of its positions, and including also relatively stationary third contact means comprising at least one contact with which said other of said elements is cooperable in another of its positions; means for connecting said first contact means and said at least one of said contacts of said second contact means to one of said main conductors; means for connecting said at least one of said contacts of said third contact means to said neutral conductor; means for connecting said terminal of each of said resistors to the other of said main conductors; and means for connecting the other terminals of said resistors to said the combinationof: a plurality of resistors constructed to operate at full heating capacity when individually connected across a predetermined pair of said conductors; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to a plurality oi. difierent positions; said switch means including relatively stationary contact means with which one of said movable elements is cooperable in two difierent positions respectively of said element; means, separate from said switch means, constructed and arranged to connect said contact means to one oi! said conductors; means, separate from said switch means, constructed and arranged to connect one terminal or each of said resistors to one 01' said conductors; and means, including additional electrical connections, so constructed and arranged that said switch means is adapted to interconnect one 'or more of said resistors and one or more of said pairs of conductors in different relationships for said plurality of diflerent positions of said switch means respectively.

1'7. In an electric heating apparatus connectable to a plurality of conductors diflerent pairs of which provide diiierent electromotive forces, the combination a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to difierent positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only oi! said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and in a succeeding position of said switch means at least one of said resistors is so supplied by certain of said conductors that it operates at less than full heating capacity.

18. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces,

the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to difierent positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates at Iull heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates at less than full heating capacity.

19. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide difierent electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive i'orce corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to diflerent positions; and means, including electrical connections, so constructed and arranged that in one position or said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and. in a succeeding position of said switch means at least two of said resistors are so supplied by certain of said conductors that each of said at least two resistors operates at less than lull heating capacity.

-20. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality oi movable elements and a common operating means for moving said elements in unison to diflerent positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates at less than full heating capacity, and in a succeeding position of said switch means at least two of said resistors are so supplied by certain of said conductors that each of said at least two resistors operates at less than full heating capacity.

21. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operatingmeans for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that in one position 01' said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating-capacity, and in a succeeding position of said switch means at least one of said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and in a succeeding position of said switch means at least one different one of said resistors is so supplied by certain of said conductors that it operates at full heating capacity.

22. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of: a plurality of resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity, and in a succeeding position of said switch means one only of said resistors is so supplied by certain of said conductors that it operates a full heating capacity, and in a sucseeding position of said switch means a different one only of said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and in a succeeding position of said switch means at least one of said resistors is so supplied by certain of said conductors that it operates at less than full heatingcapacity.

23. In an electric heating apparatus connectable to a plurality of conductors different pairs of which provide different electromotive forces, the combination of: a plurality of concentricallydisposed annular resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements'and a common operating means for moving said elements in unison to difierent posi-- tions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conductors that they operate at full heating capacity. and in a succeeding position of said switch means at least one of said resistors is so supplied by certain of said conductors that it operates at full heating capacity, and in a succeeding position 0'? said switch means at least one difierent one of said resistors is so supplied by certain of said conductors that it operates at full heating capacity.

24. In an electric heating apparatus connectable to a plurality of conductors diiferent pairs of which provide difierent electromotive forces, the combination of a plurality of concentrically disposed annular resistors constructed to operate at full capacity when electromotive force corresponding to that furnished by a predetermined pair of said conductors is individually applied thereto; switch means having a plurality of movable elements and a common operating means for moving said elements in unison to different positions; and means, including electrical connections, so constructed and arranged that in one position of said switch means at least two of said resistors are so supplied by certain of said conheating capacity.

ERNEST N. CALHOUN. 

